Virtually every industry utilizes floats for liquid-level sensing in various applications, such as fuel tanks and liquid reservoirs, where the accurate and reliable measurement of the liquid level is important. Many floats are designed to include magnets, inserts, or guiding devices, all of which aid the float in performing its function. Generally, these guiding devices, inserts or magnets are molded within the float and actually become a part of a float assembly.
Floats made of rubber materials, such as acrylonitrile rubber, are very popular because they are comparatively inexpensive, easy to manufacture into a variety of shapes and sizes and can be designed to meet a wide range of densities. Additionally, rubber-based floats are readily capable of being molded to include magnets, guiding devices, inserts, and the like, all of which aid the float in performing its function.
In spite of the aforementioned benefits of rubber-based floats, there is one significant disadvantage to their use. Rubber-based floats have a tendency to fail or degrade in the presence of various chemicals, such as acids, certain hydrocarbons, chlorinated solvents, and alcohols. Failure or degradation of rubber-based floats in these environments is the result of either or both actual chemical attack of the rubber material or absorption of the chemical by the rubber-based float. Absorption can cause the float to fail by reason of an increase in weight or by fragmentation and/or cracking of the float.
Today, many Federal, State and Municipal governments have offered financial incentives to individuals, businesses, and governmental agencies that utilize a fuel which is less polluting. One type of fuel which has gained popularity is an alcohol-gasoline blend. It has been found that use of such blends may lower a vehicle's emissions. With this key benefit in mind, many fuel manufacturers have spent considerable sums of money in developing and improving the alcohol-gasoline blends and have added alcohol-blended fuels to their product line.
As mentioned earlier, rubber-based floats are subject to partial or complete failure when utilized in conjunction with alcohols or products that are blended with alcohols. In cases where a non-alcohol compatible rubber-based float is used in conjunction with an alcohol or alcohol-blended product, the rubber material either absorbs or is attacked by the alcohol. Ultimately such absorption or attack will lead to the failure of the rubber-based float. Consequently, rubber-based floats have limited utility in these type chemical environments.
Exposure to other chemicals, such as chlorinated solvents, acids, and certain hydrocarbons, may also lead to the failure of a rubber-based float. Failure under these circumstances also occurs by attack or degradation of the float by the chemicals or by absorption by the rubber material of the chemical. Again, the inadvertent introduction of an incompatible float into a fuel tank or reservoir containing chlorinated solvents, certain hydrocarbons, or acids could lead to the failure of the rubber-based float, which in turn could result in serious, catastrophic, or possibly tragic consequences.
To date, the only means known to overcome the chemical incompatibility problems of rubber-based floats was to simply avoid their use in certain chemical environments.
As a result of the aforementioned problems in using rubber-based floats, it is the object of this invention to develop rubber-based floats which:                can be easily molded into various sizes and shapes;        can be molded to accept internal magnets, sensors, guiding devices, inserts, and the like;        are relatively easy and inexpensive to manufacture;        have use within a wide range of applications;        are resistant to attack or absorption from most chemicals, including most chlorinated solvents, hydrocarbons, alcohols, and acids;        are safe from catastrophic failure; and        effectively prevents float deterioration.        